194 HERRE 



G.^ Thallus inflated, loosely attached; whitish to bright green. 

 H. Without perforations in under surface; lobes usually with 



terminal soredia 16. physodes 



EH. With perforations in under surface; lobes longer, more 

 inflated, without terminal soredia. 



17. enter omorpha 

 GG. Thallus not inflated. 



/. Color pale, whitish or glaucous. 



/. Under side black, brown-margined; thallus expanded. 

 K. Lobes marginally ciliate; thallus medium to very 



large; glaucous white 2. perforata 



KK. Margin not ciliate; thallus small to medium; pearly 



white; maritime; i. perlata 



JJ. Under side not brown-margined; thallus narrowed 



branched. 



L. Sterile or fruiting very rarely. 

 M. Thallus beset with small or dot-like white 



soredia 6. borreri 



MM. Thallus not sorediate. 

 N. Thallus not reticulate above; margin ciliate; 



lobes very narrow, short 4. herfei ~ 



NN. Surface of thallus reticulate, margin not 

 ciliate; lobes broader, long, many- 

 cleft 3. saxatilis 



LL. Apothecia abundant; thallus adnate, bright; 



lobes narrow, sinuate 5. tiliacea . 



II. Color yellow to yellowish green. 

 O. Beneath black with chestnut or brown border. 

 P. Margin of lobes not confidently sorediate. 

 Q. Thallus smooth or isidiose-sorediate; on 



rocks 12. flavicans 



QQ. Surface wrinkled, plicate, with concolorous soredia; on 



stones, shrubs, fences 13. caper ata 



PP. Edges of lobes confidently white-sorediate; surface wrinkled, 



at least marginally 14. soredica 



OO. Beneath pale or dark, margin darker; with short, scattered, 



concolorous fibrils; surface smooth or usually more or less 



isidiose 15. conspersa 



i. PARHELIA PERLATA (L.) Ach. 



Lichen perlatus Linne, Syst. Nat. ed. 12, 712. 1767. 

 Parmelia perlata Acharius, Meth. Lich. 216. 1803. 

 Parmelia perlata Tuck. Syn. N. Am. Lich. I: 53. 1882. 

 Parmelia perlata Herre, Proc. Wash. Acad. Sci. 7: 351. 1906. 



Thallus greenish pearl-gray, dilated, membranaceous; margin 

 thin, smooth, rounded and irregularly lobulate; rest of thallus thick- 



